614 THE TEETH. 



root they remain horizontal or sometimes turn downward to a varying 

 extent. Besides the main sigmoidal curvature, each individual canaliculus 

 exhibits a more or less wavy course in its way through the dentine, and the 

 individual curvatures are, as a rule, very marked on the outer periphery of 

 the dentine. 



The dentinal canaliculi reach the outer surface of the dentine only on the 

 circumference, which is covered by enamel, while on the periphery coated by 

 cementum, including also the neck, the canaliculi terminate before reaching 

 the cementum, and are replaced by a fine, granular basis-substance greatly 

 varying in its width. The distribution of the dentinal canaliculi is in the 

 great majority of teeth uniform throughout the dentine, although exception- 

 ally I have met with specimens of dentine in which there were smaller or 

 larger territories devoid of dentinal canaliculi, which latter look as if arranged 

 in bundles or groups within the basis-substance. 



Each canaliculus contains a dentinal fiber. Longitudinal sections of den- 

 tine, stained with carmine or chloride of gold, if examined with high powers 

 from 1000 to 1500 diameters (immersion lenses) exhibit the following : 

 The canaliculi of the dentine run in a more or less wavy course through the 

 basis-substance, and are, as a rule, bifurcated only on the periphery of the 

 dentine, both toward enamel and cementum. Each canaliculus contains a 

 central, slightly beaded fiber, which on its whole periphery sends delicate, 

 thorn-like elongations through the light space between the central fiber and 

 the wall of the canaliculus. The thorns are distinctly conical, their bases 

 being attached to the dentinal fibers, and their points directed toward the 

 basis-substance. The smallest thorns spring in an almost vertical direction 

 from the dentinal fiber, while somewhat larger offshoots may run obliquely 

 through the basis-substance, and directly unite neighboring fibers with each 

 other in the vicinity of the enamel and cementum. 



The basis-substance shows a distinct net-like structure. The light spaces 

 surrounding the dentinal fibers send delicate elongations into the basis-sub- 

 stance, in which, through repeated branching, a light net-work is established, 

 the meshes of which contain the decalcified, glue-yielding basis-substance. 

 The finest offshoots of the dentinal fibers can be traced only into the mouths 

 of the elongations of the canaliculi ; on the periphery of the latter, owing to 

 their great delicacy, the offshoots are lost to sight. Coarser offshoots of the 

 dentinal fibers, at the localities mentioned before, traverse the basis-substance 

 within its light net-work, at the same time uniting dentinal fibers directly, 

 and sending slender conical offshoots into the light net-work of the basis- 

 substance. (See Fig. 262.) 



The dentinal fibers are either in direct connection with coarser offshoots 

 of the bioplasson bodies of the cementum, or the light net-work of the basis- 

 substance of the dentine is in communication with that of the basis-substance 

 of the cementum. The latter condition prevails on the periphery of the 

 neck of the tooth, where the basis-substance of the dentine is not pierced by 

 larger offshoots of the dentinal fibers, but only by a delicate net-work, 

 through which the connection between dentine and cementum is indirectly 

 established. 



In cross-sections of dentine the dentinal canaliculi are visible in the shape 

 of round or oblong holes ; the center of each is occupied by the dentinal fiber, 

 which has the shape of a small, roundish dot. Again we see that the per- 

 iphery of the dentinal canaliculus is sharply marked, and repeatedly inter- 



